Community dial office step-by-step connector



May 14, 1957 w. w. PHARls COMMUNITY DIAL. OFFICE STEF-BY-STEP CONNECTOR 17 Sheets-Sheet l Filed March l5, 1954 AGENT May 14, 1957 W. W. PHARIS COMMUNITY DIAL OFFICE STEP-BY-STEP CONNECTOR Filed March 15, 1954 17 Sheets-Sheet 2 FIG@ 2 CA LL DELAY May 14, 1957 w. w. PHARIS COMMUNITY DIAL OFFICE STEP--BY-STEP CONNECTOR Filed March l5, 1954 17 Sheets-Sheet 5 ,csi Il IF May 14, 1957 w. w. PHARE 2,792,452

COMMUNITY DIAL OFFICE STEP-BY-STEP CONNECTOR Filed March l5, 1954 17 Sheets-Sheet 4 TRUNK HUNT May 14, 1957 w. w. PHARls 2,792,452

COMMUNITY DIAL OFFICE: STEP-BY-STEP CONNECTOR Filed March 15, 1954 17 Sheets-Sheet 5 `l REVERTING CALL May 14, 1957 w. w. PHARIs 2,792,452

' COMMUNITY DIAL OFFICE sTEP-BY-STEP CONNECTOR Filed March 15, 1954 17 sheets-sheet e 60l\ (+I i ,\602 I I l 66k,L RING BACK TONE I I II I I l I aal l 612 622 l mj@ Q "*i l 652 ,5603 I I ,(062 WARNING TONE I Il I I BUSY TONE l I I I *'I,6I3 I l H \6I4 l I I IpsIs I I I I I l l slsf I I I 'I l .m' PRI. ON:621F\II I, PRLON sI-I: H) I \6Q5 l DIAL TONE I I l I I I I I I I I I I I I I I I I I I I AI I I I I I I I I RINGING SELECT A TOP BRUSH Gi l TOP I I I I I I l Irala l l I I I l I I I I I l May 14, 1957 COMMUNITY Filed March 15, 1954 TO FIG.I7

W. W. PHARIS DIAL OFFICE STEP-BY-STEP CONNECTOR SW. THRU TRK. GRE

17 Sheets-Sheet 7 olHS IND.0R PBX LINE PTY. LINES GRP.

FIG. 7

May 14, 1957 w. w. PHARIs l 2,792,452

COMMUNITY DIAL OFFICE: STEP-BY-STEP CONNECTOR Filed March 15, 1954 I 17 sheets-sheet s v TEST M J8] CONV. WARNING TONE PULSE I so' I 8llU I eozL--J- l*S812 l I I L TIM/Ne PULSE Two I ILaIa I, TIMING PULSE om; I 814 I.. l (+I Y I aISLI;` HOLD oNE I I I I I (+I I I I l l P/cKuID I n u] r/ l L CUT I 6o 1PM BAT. Y THROUG'QI I l I T I l I l I I l l I I I I 1*-805 l HoLD Two f I I I I I I I 'FIG a I I I I May 14, 1957 w. w. PHARIS COMMUNITY DIAL OFFICE STEP-BY-STEP CONNECTOR Filed March 15, 1954' 17 sheets-sheet 9 May 14, 1957 w. w. PHARIS 2,792-452 COMMUNITY DSIAL OFFICE STEP-BY-STEP CONNECTOR Filed March l5, 1954 17 Sheets-Sheet lO IOOI | I I I SEC. 0N

I I I I I I SEQONDARY I I I May 14, 1957 w. w. PHARls 2,792,452

COMMUNITY DIAL. OFFICE: sTEP-B'Y-STEP CONNECTOR Filed Maron 15, 1954 17 sheets-sheet 11 TIMING' FIG. n

May 14, 1957 w. w. PHARIS 2,792,452

COMMUNITY DIAL OFFICE sTEP-BY-STEP CONNECTOR Filed March 15, 1954 17 sheets-sheet 13 MSR (BATTERY) START TIMING START FIG.' FIG. FIG. FIG. FIG. FIG. FIG.

FIG. FIG. FIG. FIG. FIG.' 8 9 lo 1l 12 FIG. FIG. FIG. FIG. FIG. v14 l5 le 17 FIG. I8

May 14, 1957 W. w. PHARIS 2,792,452

COMMUNITY DIAL OFFICE STEP-BY-STEP CONNECTOR FIG. I4

May 14, 1957 w. w. PHARIS 2,792,452

COMMUNITY DIAL OFFICE: STEP-BY-STEP CONNECTOR Filed March 15, 19.54 17 snets-sheet 15 SECONDARY MAGNET PRIMARY MAGNET RELEASE Z153 MAGNET PRI. oN l5! MI5! Ml52 SEC. 0N 152| FIG. l5

' May 14,1957 w. w. PHARIS 2,792,452

COMMUNITY DIAL OFFICE STEP-BY-SIEP coNNEcToR Filed March l5, 1954 y 17 Sheets-Sheet 16 I l i600 l |oF le: sEc.lNT. 162

HUNT ASSIST FIG.I6

May 14, 1957 f w. w. PHARIS 2,792,452

COMMUNITY DIAL OFFICE STEP-B-Y-STEP CONNECTOR Filed Maron 15, 1954 17 sheets-sheet 17 Il 172 l l l l l PRI. INT. l7l l FIRST I DIGIT ADDING 1733 secano olerr FIG. 17

COMlVIUNITY DIAL OFFICE STEP-BY-STEP CNNECTR William W. Pharis, Rochester, N. Y., assigner, by mesne assignments, to General Dynamics Corporation, a corporation of Delaware Application March 15, 1954, Serial No. 416,018

8 Claims. (Cl. 179-18) This invention relates to automatic telephone systems and more particularly to community dial oiice stepby-step connectors for use in automatic telephone systems.

In small community dial oces which serve less than l() subscriber lines, a multi-purpose connector is utilized to complete connections between subscriber lines in the community dial office and also to complete connections to trunk lines terminating in distant oces. The P. B. X trunk hunting feature is also provided in connectors of this type so that individual subscribersV in the community dial oiiice may have several lines which are reached by dialing the same directory number.

lt is a general practice to terminate subscriber lines and P. B. X trunk line groups in the same level of the switch banks with the connector switch being directively controlled in its secondary motion to select either an individual subscriber line or the tirst trunk line of the P. B. X group. lf the first trunk line of the P. B. X

group is busy, the switch is then automatically advanced' to select an idle trunk line in the group.

It has been the practice prior to this invention to set aside a complete level of the switch banks for trunk lines leading to a distant ofiice. Since the traic between the small community dial ofrice and the distant othce usually does not warrant the use of ten trunk lines, the majority of the terminals in the level may be left vacant. If trunk line groups to more than one distant exchange are required, the ineiciency is multiplied.

It is, of course, desirable to use every available terminal in the switch banks to avoid the necessity of adding a second rank of switches when the number of subscriber lines in the exchange approaches the capacity of the switch banks.

Accordingly, it is the general object of this invention to provide a new and improved community dial oice stepby-step connector.

It is a more specific object of this invention to provide a new and improved community dial oiiice step-by-step connector which permits a more ecient use of its switch terminal banks.

Briey, the invention accomplishes the above cited objects by providing a connector which is arranged to establish connections to either trunk lines terminating in a distant oice, subscriber lines, or P. B. X trunk lines which may all terminate in a given level of its switch terminal bank. The connector circuit is arranged to normally automatically advance the switch brushes in a secondary direction to select an idle trunk line in the group of trunk lines which extend to the distant oce when the given level is selected. lf, however, a particular drop back level is dialed prior to the selection of the given level, the automatic secondary advancing means is disabled so that the switch is thereafter con-.

trolled by directive impulses for secondary advancement. A particular advantage of this arrangement is realized when restricted service is required on connections to Since the subscriber lines and the trunk lines may terminato in the same level of the switch banks, the restriction may be accomplished on a level basis rather than on a per line basis. The connector circuit is arranged to automatically advance the switch brushes to an overilow position whenever a calling subscriber line of a particular class controls the connector to select the restricted level. The automatic advancement of the brushes to overow is eiective whether the level is selected initially or after drop back from the particular drop back level. is delayed until the complete directory number of the. called line is dialed.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of this specication.

For a better understanding of the invention, reference may be had to the accompanying drawings. The drawings consist of 18 figures on 17 sheets and, when arranged according to Fig. 18, show the invention.

Fig. 1 shows the trunking diagram of the described system.

Figs. 2-17, inclusive,v show a community dial oice step-by-step connector in detailed form.

The general operation of the system can best be understood by. reference to the trunking diagram of Fig. 1. Local subscriber stations, such as Sub. 1, can extend connections to other local subscriber stations through the associated line circuit, such as local line circuit 10, line finder 40, and the connector 70. Conductors T1, R1, and S6, which terminate in the connector banks, are shown connected to local line circuit 10 for use when local line 10 is called. conductors extend to all of the local line circuits in the community dial oice.

P. B. X trunk lines terminate in line circuits, such as P. B. X line circuit 6), in the community dial oice. Connector bank terminals T3, R3, and S7 are shown connected to P. B. X line circuit 60 for use in extending a connection to the P. B. X 56. Calls originating in the P. B. X are routed through the P. B. X line circuit 60, and over conductors T3, R3, and S3 to line finder banks and thus to the connector 7 tl.

Trunk lines from the distant exchanges, such as trunkA line 25, terminate in trunk circuits, such as trunk circuit 30, in the community dial oti'ice. Local subscriber stations seize trunk circuit 30 by way of connector bank terminals T5, R5, and S5 for outgoing service.

The distant oilice operator obtains connection to subv scriber stations in the community dial oice by way of trunk line 25, trunk circuit 30, toll line circuit 20, linewhich issued September 11, 1951, and is assigned to thej' same assignee as the present invention Briey, the switch has a main set of brushes, namely, line conductors tip and ring, and control conductors sleeve and hunt sleeve,`

which move horizontally in a primary direction to'select a level of terminals and then move into the banks to select a particular set of terminals in the selected level.

The switch also has an auxiliary set of brushes X and XX. These brushes are normally positioned before a level of auxiliary contacts. The X and XX brushes move into the level of auxiliary contacts simultaneously with theprimary motion of the main brushes. Thus, the positions Patented May 14, 1957' In the latter case the automatic advancement It is, of course, understood that similarV For a detailed disclosure of this switch, reference U ing of the auxiliary brushes corresponds to the level selected by the main brushes.

The connector circuit is arranged to be dilferently controlled when different levels are selected by means of wiring of the X and XX bank contacts. Referring to'Fig. 7, it can be seen that various optional wiring maybe connected to the individual X and XX bank terminals. The various wirings of the X and XX bank terminals control the connector circuit to cause the switch brushes to either restore to normal, automatically advance in the secondary direction` to select an idle trunk line, or to remain positioned before the selected level when the level associated with the respective wiring is dialed before an unlocking level is dialed. lf the wiring causes thebrus'hes to remain positioned before the selected level, busy tone is'returned to the calling party and subsequent digits dialed into the connector are ineffective.

However, after the selection of an unlocking'leve'l, all of the above described wirings are ineffective. The switch brushes remain positioned before the selected level and the connector circuit is controlled by subsequently received directive impulses to advance the switch brushes in a secondary direction.

It is believed that it might be helpful to a more complete understanding of the invention to set Vforth in tabuf lar form the use of the various wiring of the X and XX bank terminals.

The X and XX banks are wired as follows:

N and W--Wiring on level requiring digit adding, if dialed as lirst digit, with digit canceling 'after addeddigit until the unlocking digit is dialed. N-Wiring on level requiring busy tone, if dialed before -added digit, with digit canceling after added digit until the unlocking digit is dialed.

Q--Wiring on level requiring busy tone, if dialed before added digit, and automatic trunk hunting and switch through if dialed after digit adding, but before unlocking digit.

Z-Wiring on level of unlocking digit lwith busy tone, if

dialed before first added digit.

Z and W--Wiring on level of unlocking digit to unlock either with or without added digit.

BV-Wiring on level used as prefix for busy verication by toll operator.

RS-Wiring on level restricted to line circuitsmarked byr ground on HS lead in line circuit. This level is arf ranged for automatic trunk hunting and switch through if dialed before unlocking and with contacts not used for trunk group available for regular lines.

No wiring-Levels requiring busy tone before iirst added digit and with use of level after unlocking.

vSpecial Wiring of the sleeve and hunt Asleeve terminals S and HS, respectively, in the main banks is also shown in Fig. 7. Switch through trunk groups, which are groups of trunk circuits which connect to trunk lines terminating in a distant cnice, are identified by a connection between the S andV HS terminals of the individual trunk circuits of the group. A vacant set of terminals, which serves as an all trunks busy position for the group of trunk lines, immediately succeeds the set of terminals which terminates the last trunk circuit of the trunk group. Individual or party subscriber lines are identified by the absence of a connection between the S and HS terminals. A P. B. X trunk line group is identied by ya connection between the S and HS terminals of all of the individual trunk lines except the last trunk line in the P. B.,X group.

In the drawings and description, the exchange battery is shown as plus (-1-) and minus and described as ground and battery respectively. lt is to be understood that in Vthis system the positive terminal of the battery is grounded andis, therefore, referred to as ground. The negative terminal of the battery is referred to as battery.

A detailed description of the vsystem follows.

d LOCAL CALLS Called line idle A call from a local subscriber station, such as Sub. l, to another local subscriber station will rst be described. From the preceding general description it will be understood that it is necessary to dial an unlocking digit (such as a digit corresponding to a level having Z and W Wiring on XX and X bank terminals, respectively) before the tens, units Yand ringing digits of the called subscribers line are dialed. It is to be understood that several digits may be dialed and absorbed before the unlocking digit is dialed for the purposev of achieving the well known 2-5 numbering scheme. The digit adding function of the connector is described separately in 'the latter part of the description and so is omitted from this portion of the description.

When the calling subscriber at Sub. l lifts his handset, local line circuit 10 and line finder 4? serve to connect the loop circuit closed at the subset to tip and .ring'conductors T4 and Rd, respectively, of the connector circuit.

ln response to the finding Vof the line and the resulting connection of the loop circuit to the tip and ring con ductors T4 and R4, respectively, calling bridge relay 326 operates. The operating circuit for relay 320 extends from ground through break contacts 212 on unoperated relay 210, the upper winding of relay 32), break contacts 311 on unoperated relay 31d, break contacts 211 on unoperated relay 2116, break contacts 2131 on unoperated relay 800, tip conductor T4, line iinder 4b, the iinder tip brush FT, tip conductor Ti, through the loop circuit closed at the calling subset, ring conductor Ri, line iinder ring brush FR, ring conductor'Ri, break contacts 2ti3 on unoperated relay 800, break contacts 214 on unoperated relay 2lb, break contacts Sie on unoperated relay 319, and through the lower winding of relay 320 to battery. At operated make contacts 921.2, relay 32u closes an operating circuit for relay 900.

Release delay relay 96o now operates over a circuit extending from ground on break contacts Z141 on the unoperated release magnet M153, through break contacts 1118 on unoperated relay i111), break contacts 1G44 on unoperated relay 440, break contacts d66 on unoperated relay S60, operated make contacts 97.2 on relay 324) and through its winding to battery. At its operated make contacts 301 and 3M, relay 9% shunts the break contacts 211 and 214, respectively, on uno-perated relay 2li) in thepreviously described operating circuit of relay320.

At its operated make contacts 364, relay 945i) closesground through break contacts 44 on unoperated relay 1140 to the sleeve conductor S4 to hold the switch throughl relay (not shown) of line finder iii and the cut-off relay (not shown) of line circuit iti operated in the well'known manner. At its operated make contacts Sill, relay 9% closes an operating circuit to the reverting call delay relay 210.

Relay 210 now operates over a circuit extending from the previously mentioned ground on operated make con-k tacts 931 of relay 9%, through break contacts M2 on relay 21), break contacts Sdi on unoperated relay Silit, and through its lower winding to battery. At its make contacts Sli, relay Zio locks operated to the previously described ground on the sleeve conductor S4. The monitor lamp 1,131 is now illuminated over a circuit extending' from ground on break contacts 9&2 of unoperated relay 310, break contacts dil-d of reiay 36d, operated make contacts 816 on relay Zit?, and through the lamp to battery on the MSR lead. Xt its operated make contacts V814i, relay 21d connects ground through break contacts 81H3 on relay CT to the master ground lead MG.

Responsive to the connection of Vground to thenraster ground lead MG, the primary delay relay lil operates over a circuit extending from ground on conductor MG through primary oit-normal break contacts PRI. ONQL which operate when the switch moves oit-normal inits primary direction, and through its upper Winding to battery. Secondary delay relay 1010 operates over a circuit extending from ground on the master ground lead MG, through secondary off-normal break contacts SEC. ON101, which operate when the switch is stepped otrnormal in the secondary direction, and through its lower winding to battery. Party delay relay 1020 operates over a circuit extending from ground on the master ground lead MG through overow break contacts OF102, which operate when the switch is advanced to the overow position in either a primary or secondary direction, break contacts 1042 on unoperated relay 440, ringing selecting switch off-normal break contacts RS. ON122, which operate when the ringing switch is advanced oli-normal, and through its upper winding to battery. Trunk hunting delay relay 930 is operated at this time over an obvious circuit extending from ground through operated make contacts 1021 on relay 1020.

'I'he connector is now ready to receive directive impulses as signified by the fact that dial tone is now connected to the calling party. The dial tone circuit extends from the dial tone lead of Fig. 6 through primary oinormal break contacts PRI. ON61, which operate when the switch is advanced off-normal in its primary direction, break contacts 631 on unoperated relay 1730, break contacts 621 on unoperated relay 1720, break contacts 433 on unoperated relay 1530, break contacts 0F41, which operate when the switch is advanced to an overflow position in either the primary or secondary direction, operated contacts 213 on relay 210, the upper winding of relay 320 to the tip conductor T4 and thus to the calling subscriber.

1t can be seen that this operation serves to replace thev ldirect ground through the upper winding of relay 320 to the calling line with grounded dial tone.

Assume that the calling subscriber rst dials the digit 2. The XX and X bank rterminals of level two, shown in Fig. 7, are equipped with Z and W wiring, respectively, and identify the level as an unlocking level. In response to each interruption of the calling loop circuit by the dial rspn'ngs, calling bridge relay 320 releases and, at its break :contacts 923, repeats the pulses to the combination lock j pulse and hunt assist relay 1600. Relay 900 remains :operated during impulsing because of its slow release 1characteristic. The operating circuit for relay 1600 ex- 'tends from ground on break contacts Z141 of the unoper- :ated release magnet M153, through break contacts 1113 on unoperated relay 1110, break contacts 1044 yon un- -operated relay 440, break contacts 806 on unoperated relay 800, break contacts 923 of now released relay 320,

yoperated make contacts 943 on relay 940, operated make K contacts 902 on relay 900, operated make contacts 933 .on relay 930, the upper and middle windings of relay 1600 in parallel, break contacts 1601 on relay 1600 and through break contacts Z153 on release magnet M153 to '.battery.

At its operated make contacts 1102, relay 1600 repeats` 'the impulses to the primary magnet M151. The circuit Kextends from ground on operated make contacts 1102 yon relay 1600, through operated make contacts 1023 on relay 1020, operated make contacts 1014 on relay 1010, operated make contacts 942 on relay 940, and through the primary magnet M151 to battery. This ground also extends through the lower winding of primary delay relay 940 to battery. The energizing circuit for the upper winding of relay 940 is opened by PRI. ON91 contacts when the switch takes a step off-normal but the relay is held energized over its lower winding during impulsing. Operated make contacts 1101 on relay 1600 connect ground on the master ground lead MG through SEC. 1NT.162 contacts, which operate when the secondary magnet M152 operates, through break contacts PRI. INT.171, which operate when the primary magnet M151 operates,

break contacts R.S. NT.123, which operate when theringing selecting switch stepping magnet M122 operates,

through break contacts 1215 on unoperated relay 1210,`

0 operated make contacts 933` on relay 930,' to the wind.' ing of relay 1600. through operated make contacts 1101 on relay 1600 will hold relay 1600 operated until the primary magnet M151 has had sucient time to operate, as signied by the operation of its interrupter contacts PRI. INT.171 regardless of the length of pulse delivered to relay 1600 at the break contacts 923 of the calling bridge relay 320. This is the so-called lock pulse feature which assures properoperation of the switch even though the calling bridge relay 320 is pulsed over a very long or heavily loaded subscriber line.

Relays 320 and 1600 and primary magnet M151 are operated twice in response to the dialing of the digit 2, and the switch is stepped to level two. At the termination of the second impulse, primary delay relay 940 is deenergized for suicient time to allow its release.

An operating circuit for relay 1720 is closed in response to the release of primary delay relay 940 from W wiring ground on X bank terminal 2 of Fig. 7, and through the X brush XB of the connector switch, break contacts 1731 on unoperated relay 1730, operated make contacts 1521 on relay 1020, break contacts 1442 on now released relay 940, break contacts 1721 on unoperated relay 1720, and through the winding of relay 1720 to battery. First digit adding relay 1720 operates in this circuit and closes a locking circuit for itself through its operated make contacts 1722, break contacts 1441 on unoperated relay 940 and operated make contacts 304 on relay 900 to ground.

Also responsive to the release of the primary delay relay 940, ground on master ground conductor MG is connected through break contacts 341 on relay 940 over the XX brush XXB of the connector switch, the second XX bank terminal, Z wiring, operated make contacts 1723 on relay 1720, the winding of relay 1730, break contacts 1734 on unoperated relay 1730, break conacts Z153 on release magnet M153 to battery. Second digit adding relay 1730 operates in this circuit. At its operated make contacts 1733', relay 1730 closes a ground locking circuit for itself from ground on operated make contacts 304 on relay 900, and at its operated make contacts 1735, closes a direct battery locking circuit for its winding. The ground on the XX brush XXB, which was previously described as being connected to Z wiring, is

now further connected through operated make contactsV 1737 on relay 1730, operated make contacts 1725 on relay 1720, operated make contacts 1312 on relay 210, break contacts 1303 on unoperated relay S00, break contacts 1711 on unoperated relay 1210, operated make contacts PRI. ON151 and through the winding of release magnet M153 to battery.

Release magnet M153 operates in this circuit to restore the switch brushes to normal. When the switch brushes restore to normal, primary off-normal contacts PRL ON91 reclose to reenergize the primary delay relay 940 on its upper winding. When relay 940 operates, it opens break contacts 1441 to open the previously described locking circuit for the first digit adding relay 1720 which now releases.

It is to be noted that the dialing of an unlocking level is signied by the operation of the second digit adding relay 1730 which is now locked operated. Dial tone is not reconnected to the calling party when the switch is restored to normal after selection of an unlocking level since break contacts 631 of relay 1730 effectively open' the circuit. Ground for the upper winding of calling bridge relay 320 is supplied from operated make contacts 632 of relay 1730.

Assume that the last three digits of the called subscriber line number are 971. The calling subscriber now operates his dial to transmit nine impulses. Calling bridge relay 320 releases on each impulse to operate huntV assist relay 1600 which in turn repeats the impulses to;

It can be seen that this circuitV 

